1. Field of the Invention
The present invention relates to a semiconductor laser unit, and more particularly to a semiconductor laser unit having a semiconductor element, optical components, temperature sensing components, etc., within a package.
2. Description of the Related Art
In conventional high-output semiconductor laser units, an organic adhesive such as epoxy, silicon, etc., is used for fixing a temperature sensing component such as a Peltier element, a thermistor, etc., and an optical component such as a lens, an optical fiber, etc., within a package. Furthermore, a method of sealing the package hermetically with dried air or inert gas is adapted with the object of preventing condensation within the package or preventing the entrance of dust into the package. In a conventional semiconductor laser unit shown in FIG. 6, for example, solder 16 is used in joining a laser stem 14, bonding a semiconductor laser 15, and a heat spreader 13 together to assure conductivity and heat radiation. The join between other temperature sensing components that require no conductivity, that is, the join between the heat spreader 13 and Peltier elements 12, or the join between a thermistor 19 and the laser stem 14, is performed by use of an organic adhesive 24 such as epoxy, silicon, etc.
However, the organic adhesive used for fixation of the aforementioned components generates organic gases gradually from the interior of the adhesive because of heat generation during laser operation, elapse of time, etc. Since the semiconductor laser unit is in a hermetically sealed state, the generated organic gases adhere to the lens or windowpane and change their transmission factors.
The present invention has been made in view of the aforementioned circumstances. Accordingly, it is the primary object of the present invention to provide a semiconductor laser unit which is capable of preventing a change in the transmission factor of an optical component and a reduction in the optical output due to the adhesion of a residual organic substance, etc., to the optical component, and obtaining an optical output whose reliability is high up to high output.
To achieve this end, there is provided a semiconductor laser unit comprising: a semiconductor laser chip mounted within a package; a temperature sensing component fixed within the package; and an optical component fixed within the package; wherein at least either the fixation of the temperature sensing component or the fixation of the optical component is performed with an inorganic adhesive.
In the semiconductor laser unit, the package may be hermetically sealed. It is desirable that the inorganic adhesive have at least one of alumina, zirconia, or silica as its main component. It is also desirable that the inorganic adhesive have an inorganic metal material as its main component. In that case it is desirable that the inorganic metal material be soldering material.
The aforementioned xe2x80x9ctemperature sensing componentxe2x80x9d is a component for sensing heat generated from a semiconductor chip or an optical component and then keeping the temperature of the semiconductor chip constant. The temperature sensing component has function such as cooling, heat radiation, heating, etc., or has a combined function of them and is fixed within the package along with the optical component.
The aforementioned xe2x80x9coptical componentxe2x80x9d refers to any optical component, which is used for light transmission, focusing, polarization, deflection, modulation, wavelength selection, wavelength conversion, etc., such as a lens, an optical filter, etc. The optical component used in the present invention includes a windowpane provided in a package cover.
The aforementioned xe2x80x9cinorganic adhesivexe2x80x9d is an adhesive composed mainly of an inorganic substance. More specifically, it contains an inorganic substance of 99% or greater and an organic substance of 1% or less.
The aforementioned xe2x80x9cmain componentxe2x80x9d indicates a component whose content is largest. In the case where there are a plurality of components whose content is almost largest, the main component indicates the plurality of components.
According to the present invention, at least either a temperature sensing component or an optical component is fixed with an inorganic adhesive. For this reason, organic gases are hardly generated. Therefore, the present invention is capable of preventing a change in the transmission factor of the optical component, a reduction in optical output, and occurrence of optical noise due to the adhesion of organic gases to the optical component, and obtaining an optical output whose reliability is high up to high output. The present invention is also capable of enhancing optical output more effectively if it is applied to a semiconductor laser unit where a package is hermetically sealed.